The present invention relates to a biosensor for rapid and high accuracy quantification of a specific component contained in a sample and a method of manufacturing the same.
Conventionally, there is a disclosure of a biosensor as mentioned below as the system for facilitating simplified quantification of a specific component contained in a sample without necessitating dilution or agitation of the sample solution (Japanese Laid-Open Patent Publication Hei 3-202764).
More specifically, the biosensor is manufactured by forming an electrode system comprising a working electrode and a counter electrode on an electrically insulating base plate by screen printing and the like, and subsequently forming thereon an enzyme reaction layer comprising a hydrophilic polymer, an oxidoreductase, and an electron acceptor.
If a sample solution containing a substrate is dropped on the enzyme reaction layer of the biosensor thus produced, the enzyme reaction layer is dissolved, causing reaction between the substrate and the enzyme. As a result, the substrate is oxidized and, at the same time, the electron acceptor is reduced. Upon completion of the substrate-enzyme reaction, the reduced electron acceptor is electrochemically oxidized. The concentration of the substrate in the sample solution is then determined from the current value across the electrodes during this oxidation reaction.
The biosensor having the above-mentioned structure, however, has a drawback that even if the concentration of the substrate in the sample solution is equal, there arises a difference in the measured oxidation current value depending on other components contained in the sample solution.
One possible cause is interaction between solid substances exceeding 1 .mu.m in size, such as hemocyte contained in the sample solution, and the electron acceptor reduced upon enzyme-substrate reaction. Close contact of the solid substances with the reduced electron acceptor will cause oxidation of the electron acceptor by the interaction therebetween, which leads to inaccurate measurement of the oxidation current value.
One effective measure for correcting this issue is to dilute the sample solution with a certain dilute solution in order to minimize the difference in the nature of the components contained in the sample solution. This method, however, is not necessarily advisable from the aspect of operability or controllability.